Abstract:
The subtle and cascading effects (e.g., altered interspecific interactions) that anthropogenic
stressors have on local ecological assemblages often go unnoticed but are
concerning given their importance in ecosystem function. For example, elimination
of buffalo from the Serengeti National Park is suggested to have driven increased
abundance of smaller antelope as a result of release from competition. The perceived
low abundance of small antelope in the contractual Postberg section of the West Coast
National Park (the park) has been an ongoing management concern which has been
anecdotally attributed to predation by a mesopredator (the caracal, Caracal caracal).
However, we hypothesized that the historical overstocking, and consequent overgrazing
by larger-bodied managed ungulates would influence small antelope abundance. Using
camera traps, we investigated species co-occurrence and temporal activity between
small antelope, managed ungulates and caracals in Postberg as well as another part
of the park (Langebaan) and a farm outside of the park. Results suggest that small
antelope and managed ungulates have a high degree of temporal overlap (1D 0:74,
0.79 and 0.86 for the farm, Langebaan and Postberg respectively), while temporal
partitioning between small antelope and caracal is apparent (1D0:59). Further, small
antelope and managed ungulates appear to occur independently of one another (SIF
D 0.91 1 across areas). Managed ungulates were detected almost three times more
frequently on fallow lands when compared to the more vegetated sites within the park
suggesting that segregated food/cover resources allow for independent occurrence.
Small antelope had a much higher probability of occurrence outside of the protected
area (e.g., D 0:192 and 0.486 for steenbok at Postberg, Langebaan compared to
0.841 on the farm), likely due to less variable (more intact) habitat outside of the
protected area. There is not sufficient evidence to currently warrant management
intervention for predators. The small size of the protected area provides limited scope
for spatial replication thus reducing possibilities to infer the cause and effect for
complex interactions (which would historically have taken place over much larger
areas) with negative implications for adaptive management. We recommend continued
monitoring over multiple seasons and a wider area to determine the spatial information
requirements to inform management of small protected areas.
